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CVE-2021-23980· NVD / CVE Program· CNA mozilla

A mutation XSS affects users calling bleach.clean with all of: svg or math in the allowed tags p or br in allowed tags style, title, noscrip

Noroxi assessment

Priority: Monitor (action score 24/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.48% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: python-bleach (Debian:10) 3.1.2-0+deb10u2; python-bleach (Debian:12) 3.2.1-2.1; python-bleach (Debian:9) 2.0-1+deb9u1.

Low priority for now. Upgrade to python-bleach (Debian:10) 3.1.2-0+deb10u2; python-bleach (Debian:12) 3.2.1-2.1; python-bleach (Debian:9) 2.0-1+deb9u1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A mutation XSS affects users calling bleach.clean with all of: svg or math in the allowed tags p or br in allowed tags style, title, noscript, script, textarea, noframes, iframe, or xmp in allowed tags the keyword argument strip_comments=False Note: none of the above tags are in the default allowed tags and strip_comments defaults to True.

MediumCVSS 6.1 · v3.1—No exploit Fix available
Published
Feb 16, 2023
Updated
Jun 16, 2026
EPSS
0.4% · 40th percentile

Report tools

JSON

Action score

24

Monitor

Low priority for now.

CVSS
24 / 40 · 6.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-23980

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
mozillableach

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • mozilla bleachbefore 3.3.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (mozilla). Independent of NVD's CPE analysis and usually ahead of it.

  • Mozilla Mozilla Bleach

    • unspecified and later · before 3.3.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:10python-bleachbefore 3.1.2-0+deb10u23.1.2-0+deb10u2
Debian:12python-bleachbefore 3.2.1-2.13.2.1-2.1
Debian:9python-bleachbefore 2.0-1+deb9u12.0-1+deb9u1
openSUSE:Leap 15.2python-bleachbefore 3.1.5-lp152.2.3.13.1.5-lp152.2.3.1
openSUSE:Tumbleweedpython-bleachbefore 6.4.0-1.16.4.0-1.1
openSUSE:Tumbleweedpython-bleachbefore 6.1.0-1.56.1.0-1.5
PyPIbleachbefore 3.3.03.3.0
Red Hat:ansible_automation_platform:4.2::el7automation-hubbefore 0:4.2.2-1.el7pc0:4.2.2-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python-bleachbefore 0:3.3.0-1.el7pc0:3.3.0-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python-bleach-allowlistbefore 0:1.0.3-1.el7pc0:1.0.3-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python-galaxy-importerbefore 0:0.2.15-1.el7pc0:0.2.15-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python-galaxy-ngbefore 0:4.2.2-1.el7pc0:4.2.2-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python-pulp-ansiblebefore 1:0.5.6-1.el7pc1:0.5.6-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python3-bleachbefore 0:3.3.0-1.el7pc0:3.3.0-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python3-bleach-allowlistbefore 0:1.0.3-1.el7pc0:1.0.3-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python3-djangobefore 0:2.2.18-1.el7pc0:2.2.18-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python3-galaxy-importerbefore 0:0.2.15-1.el7pc0:0.2.15-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python3-galaxy-ngbefore 0:4.2.2-1.el7pc0:4.2.2-1.el7pc
Red Hat:ansible_automation_platform:4.2::el7python3-pulp-ansiblebefore 1:0.5.6-1.el7pc1:0.5.6-1.el7pc
Red Hat:ansible_automation_platform:4.2::el8automation-hubbefore 0:4.2.2-1.el8pc0:4.2.2-1.el8pc
Red Hat:ansible_automation_platform:4.2::el8python-bleachbefore 0:3.3.0-1.el8pc0:3.3.0-1.el8pc
Red Hat:ansible_automation_platform:4.2::el8python-bleach-allowlistbefore 0:1.0.3-1.el8pc0:1.0.3-1.el8pc
Red Hat:ansible_automation_platform:4.2::el8python-galaxy-importerbefore 0:0.2.15-1.el8pc0:0.2.15-1.el8pc
Red Hat:ansible_automation_platform:4.2::el8python-galaxy-ngbefore 0:4.2.2-1.el8pc0:4.2.2-1.el8pc

+8

Same product

mozilla: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-7753An issue was discovered in Bleach 2.1.x before 2.1.3.
    40Plan
  • CVE-2020-6817bleach.clean behavior parsing style attributes could result in a regular expression denial of service (ReDoS).
    30Monitor
  • CVE-2020-6802In Mozilla Bleach before 3.11, a mutation XSS affects users calling bleach.clean with noscript and a raw tag in the allowed/whitelisted tags
    25Monitor
  • CVE-2020-6816In Mozilla Bleach before 3.12, a mutation XSS in bleach.clean when RCDATA and either svg or math tags are whitelisted and the keyword argume
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:python-bleach3.2.1-2.1 · Debian:12Package registry (OSV)
opensuse:python-bleach3.1.5-lp152.2.3.1 · openSUSE:Leap 15.2Package registry (OSV)
PyPI:bleach3.3.0Package registry (OSV)
red hat:automation-hub0:4.2.2-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-bleach0:3.3.0-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-bleach-allowlist0:1.0.3-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-galaxy-importer0:0.2.15-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-galaxy-ng0:4.2.2-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python-pulp-ansible1:0.5.6-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-bleach0:3.3.0-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-bleach-allowlist0:1.0.3-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-django0:2.2.18-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-galaxy-importer0:0.2.15-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-galaxy-ng0:4.2.2-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
red hat:python3-pulp-ansible1:0.5.6-1.el7pc · Red Hat:ansible_automation_platform:4.2::el7Package registry (OSV)
suse:python-bleach3.1.5-bp152.2.4.1 · SUSE:Package Hub 15 SP2Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records